This invention relates to the fasteners and, in particular, to a nut to be secured to a panel to form an assembly to which elements can be fastened by the use of threaded fasteners, such as screws and bolts. This invention also relates to a method of applying the nut to the panel.
Many products are manufactured from supporting panels, such as sheet metal panels, to which are attached other elements through the use of threaded fasteners. Generally, in such instances a nut is desirably secured to the supporting panel to receive the threaded fastener in a manner such that the nut is positively maintained fixed against rotation or removal from the panel in an axial direction in order that the threaded fastener can be applied in a high volume production environment with a minimum of disruption due to dislodged nuts. Such nuts and supporting panel assemblies find particular widespread application in the automotive and related industries.
Several types of nuts are well known and in common use in connection with sheet metal panels which receive threaded fasteners, such as thread forming screws, in order to secure elements to the panels or secure panels to each other. One type of such nuts, for example those shown in U.S. Pat. Nos. 2,075,675; 2,102,558; 3,304,980 and 3,361,175 have prongs for clinching the nut to a panel through which the prongs project through a hole prepunched or predrilled through the panel. Another type of nut relies upon a piercing of the panel, by means of a pilot type projection or post, and resulting flow of metal in the vicinity of the hole pierced in the panel into undercut portions of the nut to clinch the nut into position. Examples of this type of nut are shown in U.S. Pat. Nos. 3,187,424 and 3,282,315.
U.S. Pat. Nos. 3,824,675 and 3,985,172 disclose a "panel extruding nut" and a method of panel and nut assembly in which the nut body includes two bores, the first of which nearest the panel surface has a diameter larger than the other bore. A punch is used to pierce the panel member and to extrude and shape an integral neck into the larger bore to mechanically secure the nut thereon. The diameter of this bore, together with the extruded or drawn thickness of the panel member, is substantially equal to the diameter of the other bore and slightly larger than the minor diameter of the screw thread of the thread forming screw to which the nut is to be secured. The extruded neck and the nut are then threaded by the thread forming screw. This provides another type of clinched nut.
While both clinched nuts and piercing nuts have found widespread use, they possess certain disadvantages which are undesirable in many applications. The primary disadvantage is that both types of nuts lack adequate retaining capability so that the nut may become disengaged from the panel when seeking to insert a threaded fastener, either causing the nut to drop free or rotate so that the fastener cannot be properly seated. Alternatively, where the nut is properly retained there still exists a possibility of distortion and pull through upon securing of the threaded fastener. Alternatives to these types of nuts, such as riveting or welding, are also unsatisfactory and also present handling and economic problems. The basic clinch nut itself is inconvenient to use because the panel must first be handled to drill or punch the necessary holes for insertion of the nuts.